It's original definition was "Laughing out loud" (also written occasionally as "Lots of Laughs"), used as a brief acronym to denote great amusement in chat conversations.

Now, it is overused to the point where nobody laughs out loud when they say it. In fact, they probably don't even give a shit about what you just wrote. More accurately, the acronym "lol" should be redefined as "Lack of laughter."

Depending on the chatter, its definition may vary. The list of its meanings includes, but is not limited to:

1) "I have nothing worthwhile to contribute to this conversation."

2) "I'm too lazy to read what you just wrote so I'm typing something useless in hopes that you'll think I'm still paying attention."